Garda Sergeant Maurice McCabe is currently on indefinite stress-related sick leave and has no plans of returning to work while Garda Commissioner Nóirín O'Sullivan is still in place.

It wasn't always like this. Sgt McCabe had a good working relationship with Ms O'Sullivan when she took over from former Garda commissioner Martin Callinan.

She praised the Garda whistleblower for raising concerns about malpractice in the force and insisted she would introduce a culture which would encourage gardaí to come forward with concerns over work practices.

She even added him to a team tasked with establishing if gardaí were still wrongly quashing penalty points for motorists.

However, things changed during the Kevin O'Higgins Commission of Investigation into claims of garda malpractice in the Cavan/Monaghan Division.

Sgt McCabe felt Ms O'Sullivan's legal team was seeking to undermine his claims of misconduct. He also believed other gardaí were suggesting he raised concerns due to an agenda motivated by malice. Soon after the publication of the O'Higgins Report, Sgt McCabe went on sick leave.

It is not the first time Sgt McCabe has gone on stress-related leave. At the height of the penalty points controversy, he was also forced to take time off work.

Sgt McCabe claimed he was harassed and bullied by other members of the force for raising concerns about gardaí quashing penalty points and failing during investigations into serious crimes.

The controversy surrounding his allegations had major repercussions for the justice system and resulted in several key figures losing their jobs.

Former justice minister Alan Shatter was forced to step aside, as was Mr Callinan, who called Sgt McCabe's allegations "disgusting".

Former secretary general in the Department of Justice Brian Purcell was also moved during the Garda scandal.